8 solve the triangle a2556 km b2164 km c1921 km find the mea

8.
solve the triangle.

a=25.56 km, b=21.64 km, c=19.21 km

find the measure of angle A.

A=________ degrees. round to two decimal places

Solution

cosA=(b^2+c^2-a^2)/(2*b*c)

Given, a=25.56 km, b= 21.64 km, c=19.21 km

cosA= (21.64^2+19.21^2-25.56^2)/(2*21.64*19.21)

cosA=0.2213

A=cos^-1(0.2213)

Angle A=77.21 degree